Dl-Aspartic acid

DL-Aspartic acid dimethyl ester hydrochloride [14358-33-9] M 197,7, 116-117". Crystd from absolute MeOH. [Kovach et al. J Am Chem Soc 107 7360 1985.] Diethyl ester has pK 6.4. 

D-Aspartic acid, systematic name, formula, and molecular weight, 2 558t DL-Aspartic acid, systematic name, formula, and molecular weight,... 

Numerous groups have described the use of d-AAO in a variety of combinations with other agents and in a variety of processes. Cheng and Wu, in the context of a biotransformation of DL-aspartic acid to L-alanine, in which the key reaction works only with L-Asp, removed residual D-Asp with d-AAO and converted the resulting oxaloacetate into L-Asp by including L-aspartate aminotransferase (r-AspAT) in the reaction mixture (Scheme 1). 

D-aspartic acid DL-aspartic acid L-aspartate decarboxylase... 

Also Tanabe have extended the use of that aspartic acid producing process by using the L-aspartic acid as the substrate for L-alanine production using P. dacunae cells with L-aspartate decarboxylase activity. This process has been operating since 1982 using sequential colunms of iimnobihsed E. coli and P. dacunae cells (Chibata, Tosa and Takamatsu, 1987). Also, DL-aspartic acid can be used as the feed in this process. Then, D-aspartic acid is obtained as an additional product, for which there is a modest demand. 

The crude DL-aspartic acid, amounting to 58-60 g., is recrystallized from 600 ml. of hot water and yields 54 g. of pure dl-... 

The mother liquor contains too little DL-aspartic acid to justify its recovery. When the filtrate and washings are evaporated to a syrup and treated with 500 ml. of 95% ethanol, the pyridine hydrochloride dissolves completely, leaving 8-9 g. of crude glycine which yields little or no sparingly soluble DL-aspartic acid on treatment with a minimum quantity of cold water. 

The final mother liquor from the recrystallization of DL-aspartic acid yields a small quantity (about 0.5 g.) of glycine. 

The purity of the recrystallized DL-aspartic acid was established by nitrogen analysis by the Kjeldahl and Van Slyke methods. The decomposition point of this product is 325-348°. 

The above method for the preparation of DL-aspartic acid is a modification of one described by Dunn and Smart. Other methods arc the decomposition of acid ammonium malate by... 

Arsenic trichloride, 30, 96 Aryl isothiocyanates, 36, 57 Arylureas, 31, 8,10 dl-Aspartic acid, 30, 7 Atrolactic acid, 33,7 Autoclave, use of hydrogenation bomb as, 30, 42... 

B. DL-Aspartic acid. A mixture of 383 g. of the above crude product, 1 1. of concentrated hydrochloric acid, 1 1. of glacial acetic acid, and 11. of water is boiled under reflux in a 5-1. round-bottomed flask for 2-3 hours. The reflux condenser is then replaced by a fractionating column, and the mixture is slowly distilled until the temperature at the head of the column has risen to 108°. This requires about 13 hours. The distillate amounts to 1.5 1. (Note 3). 

Acetic acid Acetaldehyde Acetone L-Alanine l-Alanine ion L-Alaninate ion L-Arginine dl-Aspartic acid L-Aspartic acid L-Aspartic acid ion L-Aspartate ion Benzene Butyric acid Butyrate ion Carbon dioxide Citric acid Citrate ion Creatine L-Cysteine L-Cystine Ethanol Ethyl acetate Formic acid Formate ion Fumaric acid Fumarate ion a-D-Glucose p-D-Glucose Glycerol L-Glutamic acid L-Glutamate ion... 

DL-Aspartic Acid occurs as colorless or white crystals. It is slightly soluble in water, but insoluble in alcohol and in ether. It is optically inactive and melts with decomposition at... 

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